A liquid crystal display device comprises a display panel, a Printed Circuit Board (PCB), a driver Integrated Circuit (IC), etc. The display panel and the driver IC are connected with each other by an anisotropic conductive adhesive (ACF) through a chip on glass (COG) process, and the PCB and the display panel are connected with each other by a flexible printed circuit (FPC).
At present, the display panel increasingly has a market tendency of small thickness and high resolution. The driver IC is developed to have a number of pins and a narrow long shape and the length of the driver IC is increased to adapt to the high resolution of the display panel. The display panel is developed to have a small thickness; and for example, the thickness thereof is reduced to 0.5 mm or 0.3 mm from the previous 0.7 mm.
One of the thinning processes of the display panel is to reduce the thickness of a base substrate of the display panel by using a chemical corroding method; for example, a thickness of a common Q-panel or substrate is 1.0 mm, and the thickness thereof is reduced to 0.4 mm by the thinning process.
The fabrication process of the liquid crystal display device comprises the processes of ACF attaching, COG pre-pressing, COG pressing, FPC attaching, PCB attaching, etc. In the COG pressing process, conductive particles in the ACF are pressed between the driver IC and electrodes of the base substrate under the condition of heating, and then the ACF is cured to connect the driver IC and the base substrate together. Since the requirement on resolution is higher and higher, the length of the driver IC is longer and longer, and at the same time the thickness of the base substrate of the display panel is smaller and smaller, accordingly, after the driver IC is bonded to the base substrate and cooled, the driver IC may shrink to generate the bending as shown in FIG. 1 due to the difference of expansion coefficients of the drive IC and the base substrate, and thus two ends of the driver IC generate large stress (tension) to the base substrate. The stress may be then conducted to a display region of the display panel, so that defects such as light leakage and Mura are generated. In FIG. 1, 71 is the driver IC, 21 is the base substrate, and 51 is a lower polarization sheet corresponding to the base substrate 21.
In addition, the driver IC and the FPC are bonded to the base substrate, and the thickness of the portion of the base substrate bonded to the driver IC and the FPC generally is thinner, which is only half of the thickness of other portions of the base substrate. Accordingly, the portion of the base substrate bonded to the driver IC and the FPC is easily damaged during a falling test.
It can be seen that how to realize the non-bending attaching of the driver IC to the base substrate and no damage in the falling test on the basis of reducing thickness of the display panel becomes an urgent problem to be solved.